Too Much Vitamin A and Higher Risk of Fracture

Vitamins are considered a healthy part of a person’s diet, but a new study finds too much of a good thing may be harmful. Researchers from Brigham and Women’s Hospital in Boston say too much vitamin A may increase a woman’s risk of hip fracture.

Diane Feskanich, Sc.D., and colleagues, studied more than 72,000 women between ages 34 and 77. The reviewed records of the food the women ate, the supplements they took, and their risk of postmenopausal hip fractures. The women were part of the Nurses’ Health Study, which lasted 18 years.

Vitamin A, for the purpose of this study, encompasses a number of compounds that are required for vision, growth, reproduction, and the well being of the immune system among other functions. Animal studies have suggested too much vitamin A can have a negative effect on the skeleton.

In this study, researchers found women who took 3,000 micrograms or more of vitamin A either through food or supplements had a significantly higher risk of hip fracture. Retinol is considered the most potent source of vitamin A and appeared to have the greatest impact on the rate of fracture.

Researchers say these findings offer a reason for officials to reassess the increased fortification of foods with vitamin A, particularly from retinol. Currently, it’s recommended that men consumer 800 micrograms of vitamin A and women 700 micrograms. The recommendations say 3,000 micrograms is considered a safe level.

SOURCE: Journal of the American Medical Association, 2002;287:47-54